Faten Adel Ismael Chaqmaqchee

In this study, the occurrence of two introduced terrestrial gastropod species: Monacha cartusiana (O.F. Müller, 1774) and Cochlicella barbara (Linnaeus, 1758), in the Kurdistan Region of Iraq, was investigated. Species identifications were made based on snail morphology. Snail shells were studied to determine their chemical composition and its effect on their success and establishment in the study area. Their organic components (protein and chitin) and inorganic matrix (elements) were analyzed and their correlations were investigated. Elemental analysis was performed using inductively coupled plasma - mass spectrometry and energy dispersive X-ray fluorescence for both species and their surrounding soil. Gravimetric analysis revealed that the main shell component was calcium carbonate (CaCO3) in the form of aragonite, comprising over 96% of the shells’ mass. Proteins and carbohydrates accounted for <4% of the shells. Fourier-transform infrared spectroscopy spectral analysis confirmed the presence of chitin in its β-allomorph form. Thirty-eight elements were detected. Of which, potassium (K), strontium (Sr), and rhenium (Re) were significantly different between the two species. A highly significant correlation was found between protein and carbohydrates, and CaCO3 indicating the role of the organic matrix in the formation of the mineral component. The survival of the studied species is partly attributed to a considerable overlap in their organic and inorganic chemical characteristics, along with notable differences.

This study investigates the influence of nitrogen (N) concentration on the optical and gain characteristics of Gallium Arsenide (GaAs)/gallium arsenide (GaAs) quantum wells (QWs) based vertical-cavity surface-emitting lasers (VCSELs) using MATLAB simulations. Numerical simulations were performed how varying N content affects cavity design and optical confinement properties. The stopband behavior and resonant wavelength shift were analyzed through reflectivity spectra for different N concentrations. The results reveal a red shift in the resonance wavelength and redistribution of the electric field intensity within the cavity as the N concentration increases. Higher N concentrations reduce mirror losses. However, excessive N incorporation introduces scattering and interface imperfections, leading to increased internal losses. In addition, an increase in N percentage results in reduced optical confinement factor and material gain decrease, indicating a lower overlap between the optical field and the active area. Both the threshold density and transparency carrier density were observed to rise with N addition, implying a decrease in recombination performance. Reflection-mode spectra confirm a red shift and a reduction in gain peak with higher N content. This analysis focused on a critical design of GaNAs VCSEL structure, which makes a distinction between engineering index profiles for optimal gain overlap and adjusting the optical path length for spectral control. A N concentration in the range of 1–2% provides the optimal balance along gain enhancement, optical confinement, loss minimization, and reflection gain, which are (0.11, 0.099), (175 cm−1, 162 cm−1), and (20.26 dB, 19.66 dB), respectively, thereby providing the overall performance of GaNAs/GaAs QWsVCSELs.

This work investigates the optical performance of a distributed Bragg reflectors (DBRs) structure, designed with a Matlab program using inorganic compounds of cadmium sulfide (CdS) and magnesium fluoride (MgF2 ) with a central operational wavelength of 650 nm. Because CdS (high index) and MgF2 (low index) have very different refractive indices, the proposed DBR can reflect light effectively using fewer alternating layers. The Transfer Matrix Method simulation method indicates that the DBR structure reaches its maximum reflectivity with just six-layer pairs, emphasizing its optical efficiency and structural simplicity. A comparative analysis with other DBR structures demonstrates the superior performance of CdS/MgF2 DBR, which exhibits a broader usable stopband at around 181.82 nm, the highest bandwidth of 298.49 nm, and a relatively moderate Q-factor (2.18), indicative of an enhanced reflector response. These results establish CdS/MgF2 DBR as highly efficient reflectors that are well-suited for optical systems functioning in the visible spectrum.

Molecular sieves are used in various industries, especially petroleum and gas processing plants, as catalysts. These materials are in contact with crude oil products. After several operational years, these materials’ activities were reduced to a nonfeasible level called spent molecular sieve. Tens of tons are disposed of annually from oil and gas companies in Iraq. The paper aims to determine the kinds and amounts of toxic materials carried by the nickel oxide sulfur bed spent catalyst and then submit the suitable treatment methods, such as leaching by water, base solution, and acid solution. Aradioactive test was first done to ensure the material was free from the radioactivity array. The material was tested for nickel oxide concentration after each step of treatment. It was found that the leaching by water reduces the content by 4.5% during 24 h of leaching and 15.5% after 7 days. The leaching by alkaline sodium hydroxide 10% concentration solution reduces the content by 7% during 24 h and 14.3% after 7 days. The 10% hydrochloric acid concentration solution leaching reduces the nickel content by 10.8 during 24 h and 65.7 after 7 days. Leaching by acid solution is more efficient in the extraction of nickel oxide. The treatment method novelty is to be carried out at reasonable temperatures with high metal extraction efficiency. The research results achieved this goal of attaining extraction at an easily achievable temperature of 70°C with a relatively good extraction rate higher than 65%.

This study investigates the structure of 21 table salts that were collected from different local markets in the Kurdistan region of Iraq. The major trace elements and iodine concentrations in tablesalt are analyzed through the X-ray fluorescence (XRF) technique and the titration method, respectively. The study shows that using XRF spectral analysis, the collected table salt samples are rich in chlorine, sodium, and contain a lower percentage of bromine, strontium, tin, tellurium, and iodine. Moreover, these samples have a high percentage of sulfur and sirconium, where the molybdenum is >0.2%. Other elements such as zinc and copper are essential and found in low concentrations <0.0086% and 0.001%. Iodine is a trace element that is necessary nutrients for human life, and it is naturally present in some foods. Iodine deficiency is brought on by a lack of iodine consumption. Iodized salt is highly recommended as a source of iodine to prevent iodine deficiency disease. Iodine is added to table salt in two different ways, either through iodate or through iodine. The results show that only 25% of the salt samples have an adequate level of iodine, while the other samples have low or no iodine content. According to the World Health Organization, quality of salt depends on iodine concentration and other trace elements, which are necessary for human health.

Kidney stones are considered a severe disease that causes considerable pain and can lead to kidney failure. Dietary habits may be the reason behind the development of stones in the kidneys. Twelve kidney stone samples were collected and analyzed using an X-ray fluorescent technique along with commonly consumed foodstuffs in the Koya region of northern Iraq. It was observed that all of the stones were based on calcium element. The findings reveal that Ca, Zr, S, and Cl can be the core elements of forming kidney stones in such an area. The core elements were found to include many dietary foods commonly consumed by many in the Koya region. More studies are required, however, to see whether dietary intake may be the main cause of kidney stone formation.

Vertical-cavity semiconductor optical amplifiers (VCSOAs) are interesting devices for optical communication applications. In this work, we have studied the characteristics of gain spectra and amplifier bandwidth in reflection mode at 1300 nm GaInNAs/GaAs hot electron light emission and lasing in semiconductor heterostructure-VCSOA structure using MATLAB program. The device contains 16 Ga_0.7In_0.3N_0.038As_0.962 multiple quantum wells (QWs) in its intrinsic region; the active region is bounded between eight pairs of GaAs/AlAs top distributed Bragg reflectors (DBRs) mirror and 25 pairs of AlAs/GaAs bottom DBRs mirror. Simulation results suggest that the resonance cavity of QW of HILLISH-VCSOA is varied with temperature and number of DBRs periods. We compare the relation between the wavelength and gain at a different single-pass gain in both reflection and transmission modes. The highest gain at around 36 dB is observed in reflection mode. Moreover, we calculated the amplifier bandwidth at different periods of top mirror’s reflectivity, in which when the peak reflection gains increases, the amplifier bandwidth decreases.

Geometrical contacts of a double mesa structure with 16 rows ×15 columns arrays of top emitting GaAs based 980 nm vertical cavity surface emitting lasers (VCSELs) are fabricated and characterized. In this paper, 5 strained In0.22Ga0.78As/Ga0.9AsP0.1 quantum wells (QWs) within λ/2 thick cavity have been employed. The top and the bottom epitaxially grown mirrors are based on the linear graded Al0.9Ga0.1As/GaAs distributed Bragg reflectors (DBRs) with 20.5 and 37 periods, respectively. Static parameters including threshold currents, rollover currents, maximum optical output power and wall-plug efficiency are extracted from light out power-current-voltage (LIV) of VCSELs with fixed oxide aperture diameter of ∅~ 6 μm and various mesa2 diameters. In addition, spectral emission for 980 nm VCSELs of oxide aperture between ∅~ 6 and 19 μm and with fixed ∅~ 6 μm and different bias currents are analyzed. The highest optical output power of around 33 dBm is observed at bias current of 0.8 mA for short−reach optical interconnect applications.

This paper presents an electrical analysis of various diameters of two p-types of GaAs/Al_0.9Ga_0.1As and two p-types of GaAs/Al_0.3Ga_0.7As/Al_0.9Ga_0.1As distributed Bragg reflectors (DBRs) mirrors structure grown on undoped and on p-doped GaAs, which affects the characteristics of 1300 nm vertical cavity surface emitting lasers (VCSELs) and vertical cavity semiconductor optical amplifiers (VCSOAs). Electrical characterizations and Hall measurements of current−voltage (IV) for GaAs/Al_0.9Ga_0.1As linear DBRs and GaAs/Al_0.3Ga_0.7As/Al_0.9Ga_0.1 As graded DBRs were also performed at temperatures between 13 and 300 K. Consequently, p-type DBRs are designed with graded composition interfaces technique. The smaller mesa diameters are used to reduce vertical and longitudinal resistances and to limit the heating effect and improve the characteristics of VCSEL/VCSOA devices.